critical facultycrit-i-cal fac-ul-ty
A good working definition would be: The ability to mentally evaluate information, statements, or propositions, to determine if they are accurate, true, or likely.
dojodo-jo
A school for training in Japanese arts of self-defense, such as judo and karate.
On The Critical Faculty:“It is our only guarantee against delusion, deception, superstition, and misapprehension of ourselves and our earthly circumstances.” William Graham Sumner

One obvious problem with this approach for the authorities is that, whilst new or renewed road markings do have the merit of being cheap, they do not generate an income of a billion pounds a year.

The UK has around 6,000 speed traps. Research suggests that speed traps can lead to around a 10% fall in four common types of collision; head-on crashes, side-impacts at junctions, collisions with trees and lampposts and accidents involving cyclists or pedestrians hit by cars.

Dr Joanne Hill, the head of research at the European Road Assessment Programme (EuroRAP), has stated that dedicated lanes for turning right, or left, reduce side-impacts by as much as 80%. Anti-skid surfaces can produce a 65 % reduction in RTAs (Road Traffic Accidents) across the board, new signage up to 40% across the board and renewing road markings cuts RTAs by up to 35 per cent.

So in fact speed cameras are actually the least effective measure.

Dr Hill said: "A pot of paint doesn't cost a lot of money but the rate of return is phenomenal. A highways authority could typically save 20 fatal, or serious injury accidents, over three years just by re-lining a junction. A speed camera shouldn't be the only measure installed."

It would appear, based on cost and actual effectiveness, rather than earning potential, speed traps (‘safety cameras’) should only be the final measure installed, and then only if required on actual safety grounds.